The "Most Strengthens" and "Most Weakens" Question Types

LNAT Section A frequently asks you to identify the option that most strengthens or most weakens an argument. These questions are among the most challenging because every option may have some relevance to the argument — your task is to rank them by their logical impact and select the one with the greatest effect. This lesson teaches you the specific techniques for handling these question types reliably.

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Why "Most" Matters

The word "most" is crucial. LNAT "most strengthens" and "most weakens" questions are designed so that:

• Multiple options may be relevant — perhaps two or three options bear on the argument
• Only one option has the greatest impact — it targets the argument's core logic most directly
• Distractor options are partially relevant — they address peripheral issues, related but distinct points, or weaker aspects of the argument

Key Principle: The best answer is not simply one that is relevant — it is the one that has the greatest logical impact on the connection between premises and conclusion.

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A Hierarchy of Impact

When evaluating options, think in terms of a hierarchy:

Impact level	Description	Example
Directly addresses the key assumption	Provides or undermines evidence for the unstated premise the argument depends on	If the argument assumes causation from correlation, evidence confirming or denying the causal link
Directly supports or undermines a key premise	Strengthens or weakens the most important stated evidence	Better or contradictory data on the main evidence cited
Addresses a secondary premise	Supports or undermines less central evidence	Additional data on a supporting point
Addresses implementation, not logic	Relates to the feasibility of a recommendation rather than the argument's reasoning	Cost or practicality considerations
Tangentially related	Connected to the topic but not to the argument's logic	A related fact that does not bear on the premises or conclusion

LNAT Tip: Options that address the key assumption or the most critical premise are almost always the correct answer for "most strengthens/weakens" questions. Options about implementation, feasibility, or peripheral points are usually distractors.

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Step-by-Step Technique

For "most strengthens" questions:

1. Identify the conclusion
2. Identify the key assumption — the unstated premise the argument depends on
3. For each option, ask: "Does this make the conclusion more probable? Does it directly support the key assumption or fill the main logical gap?"
4. Rank the options by their proximity to the core logic
5. Select the option with the most direct impact

For "most weakens" questions:

1. Identify the conclusion
2. Identify the key assumption — what must be true for the argument to work
3. For each option, ask: "Does this make the conclusion less probable? Does it directly undermine the key assumption or exploit the main logical gap?"
4. Rank the options by their proximity to the core logic
5. Select the option with the most direct impact

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Worked Example 1: Most Strengthens

"Cities that have invested in dedicated cycling infrastructure — protected lanes, bike-sharing schemes, and secure parking — have seen significant increases in the number of people cycling to work. Increasing cycling reduces traffic congestion, improves air quality, and benefits public health. The UK government should therefore invest heavily in cycling infrastructure in all major cities."

Key assumption: Investing in cycling infrastructure causes more people to cycle (rather than cities that already have a cycling culture being more likely to invest in infrastructure).

Options:

A. Cycling is the most environmentally friendly form of urban transport. B. A randomised trial in which twelve comparable UK cities were divided into a treatment group (receiving new cycling infrastructure) and a control group (no changes) found that cycling commuting rates increased by 35% in the treatment cities and remained unchanged in the control cities. C. A majority of UK adults say they would consider cycling if safer routes were available. D. The Netherlands, which has extensive cycling infrastructure, has one of the highest cycling rates in Europe.

Analysis:

Option	Impact	Ranking
A	Supports the value of cycling but not the effectiveness of infrastructure investment	Low — addresses a secondary point
B	Directly confirms the causal link between infrastructure investment and increased cycling through a controlled experiment in a UK context	Highest — addresses the key assumption
C	Suggests potential demand but relies on stated intentions, which may not translate into behaviour	Moderate — suggestive but not conclusive
D	Shows a correlation between infrastructure and cycling but could reflect cultural factors	Moderate — relevant but does not establish causation

Answer: B. This is the strongest option because it uses a controlled experiment to directly confirm the key assumption — that infrastructure investment causes increased cycling. The UK-specific context and the comparison with control cities make it maximally relevant.

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Worked Example 2: Most Weakens

"The introduction of genetically modified (GM) crops has been a success wherever it has been tried. Farmers who adopt GM crops report higher yields, lower pesticide use, and greater profitability. The UK should lift its current restrictions on GM crop cultivation to benefit British farmers and consumers."

Key assumption: The benefits observed in other countries would also occur in the UK.

Options: